This invention relates to shoes, and particularly to athletic shoes having shock-absorbing soles for use with rigorous activities such as running or court sports.
A conventional athletic shoe includes an outsole, a midsole, and an upper. Such a shoe is typically designed to reduce the shock felt by the wearer during foot strike. Such reduction in shock is an important consideration in reducing the likelihood of injury by the wearer and in providing comfort to the wearer. Distance runners typically strike the ground at a force equal to 2.5 times their body weight and at a rate of 180 times per minute (90 per each foot). Basketball players can experience vertical forces greater than 10 times body weight and shear forces of twice body weight. In addition to providing cushioning, an athletic shoe should provide a stabilizing mechanism that supports and controls the foot during athletic movements such as forward running, cutting, jumping and landing. Unstable shoes may cause short or long term injury due to the excessive motion at the joints brought on by unstable materials and designs.
The cushioning in most athletic shoes is supplied through a foam midsole made from ethylene vinyl acetate (EVA) or polyurethane (PU). These materials are relatively inexpensive, easily molded, and provide ample cushioning when they are new. Other shoes have used gas-filled and liquid-filled bladders to provide the required cushioning. Both of these shoe constructions provide adequate cushioning when they are new. Fluid filled bladders continue to provide like new cushioning for the life of the shoe, assuming that the fluid remains encapsulated in the shoe. Shoe midsoles made from foams provide adequate cushioning when they are new, but quickly lose some of their cushioning ability when the air cells inside the foam suffer catastrophic failure from the application of vertical and shear forces. EVA foams have compression (compaction) set rates of greater than 50%. This means that the ability to provide cushioning is reduced by at least 50% due to compaction of the material.
In addition to cushioning, a shoe should also supply support and stability. Generally, as the materials used under foot become softer, the support and stability decrease. Harder/firmer materials lend the most support and stability. Since harder/firmer materials decrease the amount of available cushioning, providing adequate cushioning without detracting from support and stability is a challenge that requires attention to detail with respect to material choices and design.
Among the several objects and advantages of the present invention may be noted the provision of an improved shoe; the provision of a sole for a shoe which provides excellent shock absorption without reducing support and stability; and the provision of such a shoe which is generally light in weight.
Generally, a shoe of the present invention has a sole for supporting a foot of a wearer, and a shoe upper adjacent the sole. The sole includes an upper force-distribution plate portion, a lower force-distribution plate portion spaced below the upper plate portion, and at least one resilient shock-absorber element in contact with and between both the upper and lower plate portions.
In another aspect of the present invention, a shoe comprises a sole for supporting a foot of a wearer, and a shoe upper adjacent the sole. The sole includes an outsole portion spaced below the upper, and a plurality of discrete, resilient, shock-absorber elements. The shock-absorber elements are positioned between the outsole portion and the upper. Each shock-absorber element is generally circular in shape in horizontal cross-section.
Other objects and features will be in part apparent and in part pointed out hereinafter.